1. Field of the Invention
This invention relates to a detector, and, more particularly, it is concerned with a super-heat detector of a refrigerating apparatus, which detects super-heat condition of refrigerant gas flowing in a refrigerant circuit in the refrigerating apparatus.
2. Description of the Prior Art
In general, when liquid refrigerant is mixed into a conduit run within a refrigerant circuit of the refrigerating apparatus, such as, for example, into gaseous refrigerant flowing in the intake tube of a compressor, the compressor brings about liquid compression to possibly cause mechanical damage to the compressor. In order to avoid such mechanical breakage of the compressor, it is necessary to detect super-heat condition of the refrigerant gas flowing in the intake tube of the compressor so as to control or protect it against or from sucking the liquid refrigerant into it.
As the device for detecting super-heat condition of the refrigerant gas, there has so far been known one as shown in FIG. 1 of the accompanying drawing. In FIG. 1, a reference numeral 1 designates an arbitrary conduit run constituting the refrigerant circuit of the refrigerator, a numeral 2 refers to a refrigerant gas flowing in and through the conduit run, and a reference numeral 3 denotes a main body of the detector to detect super-heat condition of the refrigerant gas. A saturation pressure of the refrigerant gas is fed to the detector main body 3 through a tube 4.
A temperature of the refrigerant gas in the conduit run 1 is detected by a temperature sensing element (cylinder) 5. The interior of the temperature sensing element 5 is filled with a substance 5a which thermally expands or contracts in response to temperature of the refrigerant gas. A pressure to be exerted by expansion and contraction of this filling substance 5a is transmitted to the detector main body 3 through a capillary tube 6.
A diaphragm 7 is provided in the detector main body 3. This diaphragm 7 is subjected to deformation in accordance with a difference in pressure transmitted through the capillary tube 6 and the tube 4.
A switch contact 8 is attached to this diaphragm 7. In confrontation to this switch contact 8, a counterpart switch contact 9 is provided in the detector main body 3. Both switch contacts 8 and 9 constitute a pair so as to perform opening and closing (on-off) operations of the switch. The opening and closing operations of the switch are taken out of an electrical circuit 10 in the form of electrical signals.
In the following, operation of the conventional super-heat detector will be explained. The detector main body 3 receives, in a space 3a below the diaphragm 7, a saturation pressure P.sub.1 of the refrigerant gas 2 within the conduit run 1. On the other hand, the filling substance 5a within the temperature sensing element 5 senses the temperature of the refrigerant gas 2 to expand (or contract), and generates a pressure P.sub.2 matched with the temperature which it has sensed out. Through the capillary tube 6, the pressure P.sub.2 acts in a space 3b above the diaphragm 7.
As the result of this, the diaphragm 7 will be displaced to either upper or lower direction by the differential pressure of (P.sub.2 - P.sub.1). Therefore, by appropriate selection of the thermal expansion coefficient of the filling substance 5a in the temperature sensing element 5, it becomes possible to perform on-off operations between the switch contacts 8 and 9 when the refrigerant gas has reached a predetermined super-heat condition.
In this manner, the refrigerator can be controlled against, or prevented from, the damage by detection of the super-heat condition of the refrigerant gas flowing in and through the refrigerant circuit. Incidentally, use of bellows in place of the diaphragm 7 can also produce the same effect as mentioned above.
Since the conventional super-heat detector is constructed as mentioned above, there have been such disadvantages that the heat capacity of the temperature sensing element 5 is large, on account of which its temperature response is slow, and that, since the switch contacts 8 and 9 are of a mechanical type, the switch is difficult to find its use for any purposes other than the on-and-off control operations.